The present invention relates to a chain-like self-moving (self-propelling) robot capable of moving within a pipeline, conduit or the like for inspection and monitoring of the interior thereof and performing works within the pipeline and other. More particularly, the invention concerns a chain-like self-moving robot suited advantageously for movement within a pipeline or conduit of a relatively small diameter such as pipeline for fuel gas supply service, although the invention is never restricted to such application.
Although the robot according to the invention is excellently suited for movement within a pipeline or conduit, the robot can also move (i.e. self-propel progressively) within a groove or recess, on and along a guide rail or on a floor for the purpose of inspection and work such as repair.
The robot for inspecting the interior of a gas supply pipe having a relatively small diameter in a range of 50 to 80 mm which is employed for internal inspection of a pipeline in a fuel gas supply service system is imposed with requirements mentioned below.
(1) The robot has to be capable of moving within a pipeline at least over a distance on the order of 100 meters from the entry for inspection and returning to the entry.
(2) There may exist in the pipeline offset portions or steps (difference in level) of several millimeters to 1 centimeters in height. The robot must be able to pass such offset portion.
(3) The pipeline usually includes elbow portions bent at a right angle. The robot must be able to pass through such bent portion.
(4) The robot must be capable of performing inspection or examination as to the condition of the pipeline such as measurement of wall thickness, as occasion requires.
(5) The robot has to determine or confirm the position at which the robot is located, if required.
(6) The robot must be capable of communicating with an overground station, as occasion requires.
(7) The cross-section of a pipeline is not always of a circular form having a predetermined constant diameter but may present distortion or deformation on the order of 20%. Consequently, the robot must be able to move with an adequate margin even within a pipe deformed more or less.
In light of the requirements or conditions as imposed on the robot, an attempt to provide the robot with wheels for movement will encounter a great difficulty. For example, in order to pass the offset of 1 cm as mentioned in conjunction with the requirement (2), the diameter of the wheel must be selected greater than 2 cm. However, it is very difficult or practically impossible to provide the robot with the wheels having a diameter of 2 cm, when the robot is to be operated within a pipeline of 50 cm in diameter and deformed about 20%. Further, the robot is very difficult to pass through a curved portion such as a right angle elbow.
Besides, difficulty will be encountered in an attempt to connect a robot destined to move over a distance of 100 m or more while passing by curved or bent portions to the overground station through a cable for realizing mutual communication or supplying power to the robot. If the robot must travel over a distance of 100 m or more, pulling the cable, an excessively great traction power will be required. The traction force will increase in geometric series as the number of the elbows which the robot has to pass through is increased. In the latter case, the traction force as required for the robot will amount to several tens Kgf or more. Obviously, it is extremely difficult to implement the robot which can produce such a large traction force. Further, the robot must be provided with the inspecting device position confirming device and communication device in order to meet the aforementioned requirements or conditions (4), (5) and (6). This robot must additionally be implemented so that the conditions mentioned below can be met.
(i) The robot must be implemented in such a construction which need not trail the cable.
(ii) The robot must be realized with small cross-sectional dimension of 40 mm or less in diameter in order that the robot can operate within a pipeline having a diameter of 50 mm with taking into account the possible deformation of the pipeline.
(iii) In order to impart to the robot of the small cross-sectional dimension the functions of communication, inspection, position determination, self-moving and other, these various functions must be dispersed or distributed among divided sections of the robot. In that case, the robot must be realized in a chain-like structure in which the divided sections are linked serially one another in the form of a string.
(iv) The robot having no cable must exhibit an enhanced reliability so that failure does not occur in the course of operation of the robot.
As the system for inspecting the interior of a pipeline while moving within and along the pipeline, there may be mentioned an inspection pig system of corrosion detection for pipeline [refer to Nippon Kokan Technical Report No. 99, (1983)]. The inspection unit called the pig of the known inspection pig system is designed to examine or check the wall thickness of a pipeline while moving within the pipeline. However, the inspection unit itself is not imparted with self-propelling capability but moved under a pushing force exerted by a fluid medium flowing through the pipeline. Because of the pig moving or propelling mechanism, the location where the inspection unit is placed within the pipeline differs from the location where the unit is recovered.
Further, Japanese Patent Application Laid-Open No. 10042/1972 filed Oct. 12, 1971 claiming priority based on U.S. patent application Ser. No. 79859 filed Oct. 12, 1970 now U.S. Pat. No. 4,006,359 under the title "Pipeline Crawler" discloses an inspection apparatus having a self-propelling function. However, the disclosed inspection apparatus is designed for the purpose of inspecting a pipeline having a large diameter. The self-moving mechanism of this known inspection apparatus includes legs equiped with respective wheels, wherein the inspection apparatus advances by moving the legs. Consequently, the inspection apparatus is necessarily of a very complicated structure of a large size.
Japanese Patent Publication No. 14188/1981 filed July 28, 1975 by Mitsubishi Heavy Industry Co., Ltd. under the title "INTER-PIPE TRACTION APPARATUS" discloses an apparatus which moves within a pipeline under the action of expansion and contraction of the apparatus itself which are brought about by making use of compressed air.
Additionally, Japanese Patent Publication No. 51626/1982 filed May 4, 1976 by the same applicant under the title "Intra-Pipeline Crawling Apparatus" discloses a crawling or self-moving mechanism which includes stopper means and a hydraulic piston apparatus. In the case of the last mentioned two piror art apparatuses, the stopper means are pressed against the inner wall of a pipeline while the inspection apparatus is moved in the meantime. For operation of the apparatus, it is required that the inner wall of the pipeline presents a smooth surface free of offset portions. Further, the stopper means are susceptible to be obstructed by joints of the pipes or bends or elbows of the pipeline, giving rise a problem in respect to the self-moving function and hence maneuverability of the inspection apparatus.